It is common in the prior art to equip a lawn or garden tractor with a seat switch that allows the operator's presence on the seat to be monitored. If the lawn or garden tractor is running and the operator steps off the tractor, there is a danger that the operator will be seriously injured by the blade or the power take off of the tractor. To reduce the hazard of such serious accidents electrical circuits are used to disable the engine if the tractor's blade and/or power take off is engaged and the operator steps (or falls) from the tractor seat. One example of such a circuit is found in prior art U.S. Pat. No. 5,190,019 to Harvey which issued on Mar. 2, 1993.
The '019 Harvey patent discloses a seat switch that in combination with other switches forms a circuit that can disable a magneto energized spark plug on a lawn or garden tractor. The seat switch of the Harvey patent is of a design that is closed when the operator is seated on the seat and opens in the event the operator leaves the seat. As noted in the Harvey patent, the circuit does not necessarily deactivate the engine but does so if a dangerous situation is sensed. The disclosure of the Harvey patent is incorporated herein by reference.
Normally open switches suitable for use in the circuit disclosed in the Harvey '019 patent are known in the prior art. U.S. Pat. No. 4,839,478 to Howard discloses a push button switch having a push in plunger that actuates the switch. For a normally open switch, actuation of the plunger causes the switch contacts within a switch housing to be bridged by a conductive spring that is biased against inner, opposed surfaces of the switch contacts. The disclosure of the '478 patent to Howard is incorporated herein by reference.
U.S. Pat. No. 4,795,8651 to Howard which issued on Jan. 3, 1989 discloses a safety switch mounting assembly for positioning a switch on a seat pan. The assembly includes a base for mounting the assembly, a cover that moves in response to the presence of a vehicle operator on the seat and an actuator that moves with the cover to open and close switch contacts inside an actuator housing. The contacts of the switch can be normally open or normally closed. The disclosure of the '865 patent to Howard is incorporated herein by reference. The seat switch base shown in the '865 patent to Howard includes two holes that extend through the base and allow the base to be mounted to the seat pan.
U.S. Pat. No. 5,124,512 to Huettner et al discloses a seat assembly for a utility vehicle. The seat base assembly includes a base portion, a seat cushion and a switching device for switching on and off an electrical circuit.
U.S. Pat. No. 3,829,803 to Maeda discloses a detecting device that includes a pressure receiving member and a magnetically actuated switch coupled to a bracket that supports the pressure receiving member. The device is mounted on a seat spring of a vehicle seat. The so called pressure receiving member is coupled to a bracket that engages a vehicle seat spring. The engagement between the bracket and the pressure receiving member is via a bayonet coupling.